Orexins are a family of homologous peptides including species orexin A, or OR-A, and orexin B, or OR-B. Orexin A is a 33 amino acid peptide and orexin B is a 28 amino acid peptide (Sakurai T. et al., Cell (1998), 92, 573-585). Orexins are produced in neurons of the lateral hypothalamus and bind to at least two distinct G-protein-coupled receptors, termed OX1 and OX2 receptors. The receptor OX1 is selective for OR-A, while the receptor OX2 can bind both OR-A and OR-B. Orexins are found to stimulate food consumption, regulate states of sleep and wakefulness, and may be involved in neural mechanisms of drug abuse and addiction.